Communications devices such as mobile telephones and personal computers can be used to make telephone calls and send Short Message Service (SMS) messages. The user typically has a subscription with a network provider, who charges the user for calls made or SMS messages sent.
As devices such as mobile telephones become more complex, they can run increasingly complicated software. A problem arises when a software application attempts to place a call or send a SMS message. The call or SMS message may be sent to a telephone number for which a premium charge is billed to the user. This may be without the user's consent if the user is not aware that the software application is placing such a call or sending such a message. Alternatively, it may be with the user's consent, but the user may not be aware that the call/SMS message is sent to a premium rate telephone number.
Software applications use an application called a dialer to place calls or send SMS messages. A dialer may be included as part of software installed by the user. For example, a user may install an application that includes an embedded advert. By clicking on the advert, the dialer is activated which dials a premium rate telephone number. It may not be apparent to the user that clicking on the advert causes the dialer to dial a premium rate telephone number, or that the number is a premium rate telephone number, and so the user may click on the advert several times. He will only be aware that this caused the dialer to call a premium rate telephone number when he is billed, and the bill includes the premium rate charges.
One way to prevent an application from contacting premium rate telephone numbers, either by calling or using SMS, is to use call barring. Many network operators offer a call barring service to their subscribers. The call barring service prevents calls or SMS messages being sent to premium telephone rate numbers. While this effectively stops software applications from contacting telephone premium rate numbers, it also stops the user from contacting a premium telephone rate number that he wishes to contact, and will stop legitimate applications from contacting premium rate telephone numbers. An example of a legitimate application is a call manager application which the user may, for example, programme to send an automatic SMS reply to a received SMS message.
Another way to address the problem is to compare the telephone number that the application is attempting to contact with a blacklist of telephone numbers. If the telephone number matches a telephone number in the blacklist, then the contact is not established. However, this relies on a premium rate telephone number being provisioned in the blacklist.